Fabrication of solar cells with electrically conductive polyimide adhesive

Abstract

The present disclosure provides a method of manufacturing a solar cell including: providing a first substrate and a second substrate; depositing on the first substrate a sequence of layers of semiconductor material forming a solar cell including a top subcell and a bottom subcell; forming a back metal contact over the bottom subcell; applying a conductive polyimide adhesive to the second substrate; attaching the second substrate on top of the back metal contact; and removing the first substrate to expose the surface of the top subcell.

The invention claimed is: 
     
       1. An inverted metamorphic multijunction solar cell comprising:
 a sequence of layers of semiconductor material forming an inverted metamorphic multijunction solar cell including a top subcell and a bottom subcell; 
 a back metal contact disposed on the bottom subcell; and 
 an electrically conductive substrate attached to the back metal contact with a cured electrically conductive polyimide adhesive, wherein the electrically conductive substrate comprises a metallic flexible film comprising a molybdenum layer. 
 
     
     
       2. The solar cell of  claim 1 , wherein the electrically conductive polyimide adhesive comprises carbon black particles. 
     
     
       3. The solar cell of  claim 2 , wherein the carbon black particles have a size of less than or equal to 5 micrometers. 
     
     
       4. The solar cell of  claim 1 , wherein the electrically conductive polyimide adhesive comprises silver flakes. 
     
     
       5. The solar cell of  claim 1 , wherein the cured electrically conductive polyimide adhesive has a resistivity from 100 Ω-cm to 3000 Ω-cm. 
     
     
       6. The solar cell of  claim 1 , wherein the electrically conductive substrate is a flexible substrate. 
     
     
       7. A solar cell comprising:
 a sequence of layers of semiconductor material forming a solar cell including a top subcell and a bottom subcell; 
 a back metal contact disposed on the bottom subcell; and 
 an electrically conductive substrate attached to the back metal contact with a cured electrically conductive polyimide adhesive, wherein the electrically conductive substrate comprises a metallic flexible film comprising a molybdenum layer. 
 
     
     
       8. The solar cell of  claim 7 , wherein the electrically conductive polyimide adhesive comprises carbon black particles. 
     
     
       9. The solar cell of  claim 8 , wherein the carbon black particles have a size of less than or equal to 5 micrometers. 
     
     
       10. The solar cell of  claim 7 , wherein the electrically conductive polyimide adhesive comprises silver flakes. 
     
     
       11. The solar cell of  claim 7 , wherein the cured electrically conductive polyimide adhesive has a resistivity from 100 Ω-cm to 3000 Ω-cm. 
     
     
       12. A solar cell comprising:
 a sequence of layers of semiconductor material forming a solar cell including a top subcell and a bottom subcell; 
 a back metal contact disposed on the bottom subcell; and 
 an electrically conductive substrate attached to the back metal contact with an electrically conductive polyimide adhesive, wherein the back metal contact comprises molybdenum. 
 
     
     
       13. The solar cell of  claim 12  wherein the back metal contact comprises a sequence of metal layers selected from the group consisting of Ti/Au/Mo/Ag/Au, Ti/Au/Mo/Ag, and Ti/Mo/Ag. 
     
     
       14. An inverted metamorphic multijunction solar cell comprising:
 a sequence of layers of semiconductor material forming an inverted metamorphic multijunction solar cell including a top subcell and a bottom subcell; 
 a back metal contact disposed on the bottom subcell, wherein the back metal contact comprises a sequence of metal layers selected from the group consisting of Ti/Au/Mo/Ag/Au, Ti/Au/Mo/Ag, and Ti/Mo/Ag; and 
 an electrically conductive substrate comprising a metallic flexible film comprising molybdenum attached to the back metal contact with a cured electrically conductive polyimide adhesive comprising silver flakes and/or carbon black particles having a size of less than or equal to 5 micrometers, 
 wherein the cured electrically conductive polyimide adhesive has a resistivity from 100 Ω-cm to 3000 Ω-cm.